Receivers in mobile radio systems are designed to demodulate signals arriving via multiple propagation paths. The multipath environment observed at the receiver is a result of both path generating diversity schemes and mobile radio channel effects. Diversity schemes include signal transmission from different cellular base station sites (sectors) and/or multiple antennas. These transmitted signals are subject to reflection from terrestrial objects such as landscape, buildings, and cars resulting in a time varying multipath channel. Each multipath channel path is subject to a different time varying propagation delay, attenuation, and phase shift. These paths interact with each other to create constructive and destructive interference. Interference is also caused when signals from multiple sources, which are not orthogonal to one another, arrive at a receiver.
Mobile radios have a finite set of system resources with which to demodulate the received signal. The process by which these demodulation resources are assigned to receive paths is referred to as radio control or finger assignment.
Advanced receivers such as equalizers and interference cancellers offer the possibility of mitigating the interference present in the signal.
Advanced receivers are an attractive feature in such receivers since they enable interference mitigation and can provide improvements in data rates and/or capacity for the network. However, performance issues and resource constraints necessitate the development and use of methods for controlling advanced receivers, since the advanced receiver portion of the receiver also usually has a finite set of system resources with which to perform operations such as symbol estimation, equalization, and interference cancellation.